Dana’s online neuroscience magazine Cerebrum has a fantastic article on trauma and dissociation – the splitting of consciousness that apparently makes some aspects of the mind inaccessible to others.
Dissociation is a term that’s used rather loosely in modern psychology and psychiatry. It is sometimes used to be synonymous with derealisation or depersonalisation, describing a feeling of being detached from reality or not being ‘grounded’ in your usual sense of self.
However, in its original and most interesting formulation by the French psychiatrist Pierre Janet, it describes the splitting of consciousness so one part of conscious experience is compartmentalised, becomes inaccessible, is literally ‘dis-associated’ from the rest.
Its not clear why it occurs, but Janet’s theory (often erroneously ascribed to Freud) suggests its a defence against psychological distress. Like the mental equivalent of brushing something under the carpet until you’re unaware it existed or you even did the brushing.
Regardless of whether it is genuinely a ‘defence’ in this sense, it is thought to be at play in conversion disorder, where a person might experience paralysis despite having no damage to the muscles or nervous system (so called ‘hysterical paralysis’).
There is now growing evidence that the high level control systems in the brain deliberately inhibit the movement in the immobile limb, outside the conscious control of the patient.
It is also thought to be the mechanism by which hypnosis has its effect on those susceptible to it. In this case, however, it is a form voluntary dissociation guided by suggestion – meaning someone can have the experience of, for example, limb movement without the associated sense of having willed the action.
One of the most striking demonstrations of this form of dissociation is where some people can be hypnotised not to be bothered by pain, despite the fact they can report on its intensity – even to the point of surgical operations being possible without anaesthetic in some rare cases.
Perhaps it’s not surprising then that dissociative disorders, where patients are seemingly permanently dissociated from their memory (dissociative amnesia) or dissociated from their senses or actions (conversion disorder) are particularly linked to trauma.
The most controversial of these syndromes is what used to be called ‘multiple personality disorder’, but is now called ‘dissociative identity disorder’ to suggest that the patient’s very personality structure has become dissociated from itself, seemingly leading to several identities or ‘alters’.
It’s partly controversial because it was so obviously over-diagnosed in a period of 1950s and 60s American psychiatry that was seemingly drunk on Freudian theory without recourse to the strong coffee of scientific testing.
But its also controversial because its so rare despite still being in the diagnostic manuals. For example, I’ve never met a patient with the condition, and I’ve never met anyone who’s met a patient with the condition, whereas I’ve seen many patients with dissociative amnesias and conversion disorders.
The Cerebrum opens as if it’s about ‘multiple personality disorder’ but don’t be fooled – it’s actually a really good review of what cognitive science has told us about how trauma might cause dissociation (almost all the research mentioned is on memory rather than ‘multiple personalities’).
This is still a controversial area but the article gives the case for the link. The article presents evidence that experience of childhood abuse, both physical and sexual, may be particularly linked to dissociation, perhaps suggesting that it arises from an attempt at a ‘defence’ in some cases.
Cognitive scientists are now increasingly interested in dissociation and hopefully this new level of interest should unlock some of the its mysterious secrets.
Link to article ‘Coming Apart: Trauma and the Fragmentation of the Self’.